Bottom Line:
The knockdown of LvLRRFIP2 by RNA interference resulted in higher cumulative mortality of L. vannamei upon V. parahaemolyticus but not S. aureus and WSSV infections.The expression of L. vannamei AMP genes were reduced by dsLvLRRFIP2 interference.These results indicate that LvLRRFIP2 has an important function in antibacterials via the regulation of AMP gene expression.

Mentions:
Seven LvLRRFIP2 variants, namely, LvLRRFIP2A, LvLRRFIP2B, LvLRRFIP2C, LvLRRFIP2D, LvLRRFIP2E, LvLRRFIP2F, and LvLRRFIP2G, were found. The sequences at 5′ end of LvLRRFIP2G were distinct from that of the other six LvLRRFIP2 variants. The 5′ end sequences of LvLRRFIP2A, LvLRRFIP2B, LvLRRFIP2C, and LvLRRFIP2D were identical. Both LvLRRFIP2E and LvLRRFIP2F have the same 5′ end sequences, which were different from that of LvLRRFIP2A-D. The sequence details of these seven variants of LvLRRFIP2 are shown in Fig. S1 and Table 2. Multiple sequence alignment shows that LvLRRFIP2s are highly conserved with each other (Fig. 1A). The amino acid sequence was analyzed using the SMART program to determine the structural domains of LvLRRFIP2. All LvLRRFIP2s have a DUF2051 domain (Fig. 1A), which was found in a dsRNA binding protein named DUF2051, a novel protein that interacts with the LRR domain of human FliI protein [29]. The identities among LvLRRFIP2s ranged from 44% to 97% (Table 3). Compared with the LRRFIP2 proteins from other species, LvLRRFIP2 shares a 35% to 51% identity with the LRRFIP2 proteins from insect to human (Table 4). A phylogenetic tree was constructed to determine the evolutionary relationship of LvLRRFIP2 with other known LRRFIP2 molecules. The phylogenetic tree showed that LvLRRFIP2 belonged to the invertebrate group and was closely related to LRRFIP2 in L. salmonis, Aedes aegypti, Acromyrmex echinatior, Ixodes scapularis, and Nasonia vitripennis, which are all arthropods (Fig. 1B).

Mentions:
Seven LvLRRFIP2 variants, namely, LvLRRFIP2A, LvLRRFIP2B, LvLRRFIP2C, LvLRRFIP2D, LvLRRFIP2E, LvLRRFIP2F, and LvLRRFIP2G, were found. The sequences at 5′ end of LvLRRFIP2G were distinct from that of the other six LvLRRFIP2 variants. The 5′ end sequences of LvLRRFIP2A, LvLRRFIP2B, LvLRRFIP2C, and LvLRRFIP2D were identical. Both LvLRRFIP2E and LvLRRFIP2F have the same 5′ end sequences, which were different from that of LvLRRFIP2A-D. The sequence details of these seven variants of LvLRRFIP2 are shown in Fig. S1 and Table 2. Multiple sequence alignment shows that LvLRRFIP2s are highly conserved with each other (Fig. 1A). The amino acid sequence was analyzed using the SMART program to determine the structural domains of LvLRRFIP2. All LvLRRFIP2s have a DUF2051 domain (Fig. 1A), which was found in a dsRNA binding protein named DUF2051, a novel protein that interacts with the LRR domain of human FliI protein [29]. The identities among LvLRRFIP2s ranged from 44% to 97% (Table 3). Compared with the LRRFIP2 proteins from other species, LvLRRFIP2 shares a 35% to 51% identity with the LRRFIP2 proteins from insect to human (Table 4). A phylogenetic tree was constructed to determine the evolutionary relationship of LvLRRFIP2 with other known LRRFIP2 molecules. The phylogenetic tree showed that LvLRRFIP2 belonged to the invertebrate group and was closely related to LRRFIP2 in L. salmonis, Aedes aegypti, Acromyrmex echinatior, Ixodes scapularis, and Nasonia vitripennis, which are all arthropods (Fig. 1B).

Bottom Line:
The knockdown of LvLRRFIP2 by RNA interference resulted in higher cumulative mortality of L. vannamei upon V. parahaemolyticus but not S. aureus and WSSV infections.The expression of L. vannamei AMP genes were reduced by dsLvLRRFIP2 interference.These results indicate that LvLRRFIP2 has an important function in antibacterials via the regulation of AMP gene expression.